You’ve been cutting down on fat, controlling carbs and exercising five days a week. So why aren’t you losing weight? From physical factors (age and genetics) to self-sabotage (eating mindlessly), here are 9 things that will derail your quest for a slimmer body...

You’re no slacker when it comes to your health: You exercise, watch what you eat, use portion control and resist Ben & Jerry’s without a problem.

Yet the scale needle still won’t budge.

Why are so many dieters destined to regain lost weight or never lose anything at all? Here are 9 reasons your body isn’t behaving:

1. You don’t have enough muscle.
The more muscle you have, the more calories you burn. Muscle tissue consumes more calories than fat tissue even when you’re at rest, says the American Council on Exercise (ACE).

That's why men burn calories a lot faster than women; they have more muscle.

What to do: Lift weights. You don’t have to get huge, but building and maintaining muscle week after week, year after year makes a difference in the long run.

Registered dietitian and certified personal trainer Marci Anderson has her clients alternate between strength exercises and heart rate-raising cardio in each session.

“That way, their strength training includes the calorie-burning effect of cardio,” Anderson says.

2. You inherited a “fat gene.”
If both parents are obese, you are much more likely to be obese, says Jill Comess, M.S., R.D., food science and nutrition program director at Norfolk State University in Virginia.

“A child with one obese parent has a 50% chance of being obese. When both parents are obese, their children have an 80% chance of obesity,” according to the University of California San Francisco Medical Center.

What to do: You’re not doomed. Your “genes are not [your] destiny,” according to the Harvard School of Public Health.

A 2011 study published in PLoS Medicine found that you can blame only about 2 pounds on “fat genes.” And even if you have a genetic predisposition to being overweight, regular exercise will reduce its effect by 27%.

“Losing even just a few pounds makes you healthier and less likely to develop diabetes, high blood pressure, heart disease and cancer,” Comess says. “So you don’t have to be super-slim to improve your health.”

If an overweight woman loses even 5%-10% of her total body weight, she has a greater chance of reducing or getting off her high blood pressure or other meds, she adds.

3. You’re getting older.
A sluggish metabolism is a common aging problem. In fact, our basal metabolic rate decreases about 1%-2% per decade (which translates to burning about 150 fewer calories a day) after age 20, according to ACE.

And we make matters worse by our sedentary lifestyles: sitting in traffic, long hours at the office and in front of computers.

All this inactivity means we gradually lose muscle and increase body fat, resulting in a metabolic slump. But it’s not unbeatable.

What to do: Your eating and exercise habits probably affect your weight more than the candles on your birthday cake.

Red meat, processed meats, potato chips and potatoes account for much of the weight gain among people as they age, says the Mayo Clinic. “Liquid calories” – alcoholic beverages, fruit juices, and sugar-sweetened drinks – are also at fault for gradual weight increases over the years. Even diet soda can make you fat.

People who eat more fruits, veggies, nuts and whole grains aren’t as likely to let weight creep on, year after year.

Also, don’t underestimate the power of moving. Even if you faithfully walk the treadmill for an hour each day or go to yoga class, what are you doing the other 23 hours?

Build in small movements throughout the day: Sweeping the floor, walking to a co-worker’s desk and cooking dinner burn more calories than just watching TV, emailing your co-worker or driving to the pizza joint.

4. Deep inside, you’re a cavewoman.
To survive in the days before food was readily available, the human body evolved coping strategies – slowing the metabolism, storing body fat, and stimulating the appetite when body weight was lost. The idea was to prevent dying of starvation when humans didn’t have enough to eat.

Now that food isn’t scarce, these biological processes can work against us, explains Jim Anderson, M.D., co-author of The Simple Diet (Berkley Books) and Professor Emeritus, Medicine and Clinical Nutrition at the University of Kentucky.

“The intestines make about two dozen hormones – some that stimulate eating and others that decrease the need to eat,” says Anderson, who directed the University of Kentucky’s Weight Management Program for 25 years.

What to do: You can’t fight evolution, so you have to focus extra-hard on those things you can. Be active every day and fill up on low-calorie foods, such as broccoli, carrots, tomatoes, green beans and other non-starchy vegetables.

5. Your medicine cabinet is to blame.
A host of drugs that treat diabetes, depression, high blood pressure, inflammatory disease and more affect weight regulation. Some will make you hungrier and others stimulate your body to store fat. And if a drug affects the brain, there’s a good chance it affects weight, Anderson says.

What to do: Ask your health care provider if an alternate drug or a lower dose could work, but don’t change your medications without discussing it first.

6. You underestimate your portion sizes and calories.
Almost everyone underestimates the amount of calories they take in. It’s no wonder that our bodies – along with our meals – have become “super-sized.”

The National Institutes of Health’s website, MyPlate.gov, notes that 20 years ago an average cup of coffee, served with whole milk and sugar, contained 45 calories. Today’s 16-ounce mocha contains a whopping 350 calories.

Fast-food diners underestimated the calorie count of their meals by an average of 20%, according to a 2013 Harvard Medical School study of 3,400 people who ate at McDonald’s, Burger King, Wendy’s, Subway and other chains.

And the bigger the meal, the more out of whack their calorie estimation.

Even when the restaurants posted the calorie counts and other nutrition information, 95% of the diners said they didn’t notice or pay attention to the information.

What to do: Follow the MyPlate guidelines for several days. Use measuring spoons, measuring cups and a food scale to guide you. Then plug in your food choices on that site or another reputable one to calculate your calorie intake. And read every food label for serving size and calories.

The Mayo Clinic suggests using visual cues to make portion-control easy – no measuring cups needed. For example, a single 110-calorie serving of protein (piece of skinless chicken or hamburger patty) should be about the size of a deck of cards. A serving of pasta is about a half-cup – same size as a hockey puck.

Need more help? Visit eatright.org to find a registered dietitian in your area.

7. You eat mindlessly or when distracted.
Do you eat dinner in front of the TV? Do you stop eating when you’re full – or do you keep munching until the show is over?

All too often, mindless distractions lead to more and more mouthfuls of pasta or potatoes.

If you’re munching from a bag of chips or a box of crackers, you can’t keep track of how much you’ve eaten.

You’re also more likely to feel unsatisfied if you mindlessly munch – causing you to eat more later. For example, people who ate lunch while playing computer solitaire felt less full after their meal than those who were not distracted, according to a 2011 study published in The American Journal of Clinical Nutrition.

The solitaire-playing group also was less likely to remember what they had for lunch, and when offered snacks a half-hour later, it ate 100% more than those who enjoyed lunch without distraction, say the researchers from the University of Bristol.

What to do: You can beat mindless eating, says Brian Wansink, Ph.D., who has conducted research on mindless eating as director of the Food and Brand Lab at Cornell University.

You can lose up to 2 pounds a month by making simple changes such as these, Wansink says:

“My motto when it comes to eating is “moderation,” says registered dietitian Beth Cecil, in her blog for Owensboro Health in Kentucky. “There are no ‘good’ or ‘bad’ foods. There are just some foods that you need to eat less often or in smaller amounts than others.”

Denying yourself from enjoying tasty treats can backfire, Cecil says. “Over time these restrictions can lead to cravings, binges and overeating.”

What to do: Cecil suggests you ask yourself these questions:

Do you feel guilty when you eat your favorite foods that are high in calories?

Do you crave foods you have labeled as “bad” on a regular basis?

Do you label foods as “good” and “bad”?

Do you eat your favorite foods only if you feel you deserve them?

Are you constantly watching what you eat?
Do you ever feel out of control when eating?

If you answer “yes,” you are depriving yourself. It’s time to say “yes” to your faves – but do it smartly.

Instead, cut other foods out of your diet. Stop eating foods you don’t like (even if they are “fat-free” and “low-calorie). Hate fat-free mayo? Use the regular kind, but smaller servings, Cecil says.

“Eat what you really desire, but just practice moderation,” she says.

So enjoy that glazed doughnut – but just one. If you want another, it will still be there tomorrow. After all, doughnuts or candy bars or pizza or whatever won’t drop off the face of the earth.

9. You overestimate your calorie burn.
Gym machines (especially elliptical trainers) are notorious for overestimating the calories burned by exercisers, and dieters can easily out-eat their workouts. Your 30-minute power walk might burn 200 calories, but that won’t make up for your after-exercise power smoothie.

And if you think housework equals workout, think again. In a 2014 study of 4,600 people, those who reported doing the most housework were heavier than those who got their physical activity in other ways, say researchers from the University of Ulster in the UK.

What to do: Exercise is an important tool in controlling your weight and maintaining good health, but stop rewarding your good work with food.

If you’re tempted to follow a sweat session with a smoothie or muffin, consider these numbers first:

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